Positive Active Material Phase Segmentation for High-Voltage Cycling

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Solution Overview

Problem

Lithium-ion batteries face challenges in maintaining cycle performance at high voltage due to structural instability and volume expansion issues in positive active materials, particularly with the P63mc crystalline phase structure, which leads to reduced stability and capacity.

Innovation Solution

A positive active material with a cross-section comprising a first region of P63mc crystalline phase and a second region of R3m, P2/m, or P3m1 crystalline phase, with a controlled area ratio and inclusion of elements like Co, F, and M/T elements, to stabilize the structure and reduce volume expansion during lithium intercalation and deintercalation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the P63mc crystalline phase structure is used to achieve high voltage operation, then the energy density is improved, but the structural stability deteriorates due to strong repulsion causing considerable expansion or shrinkage

Engineering Contradiction:

Improveenergy densityVSAvoidstructural stability

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The positive active material is divided into two distinct regions: a first region with P63mc crystalline phase structure that provides high voltage operation and energy density, and a second region with R3m, P2/m, or P3m1 crystalline phase structure that provides structural stability. This segmentation allows each region to perform its specialized function, resolving the contradiction between energy density and structural stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent creates a composite material system where two different crystalline phase structures coexist within the same positive active material particle. The P63mc phase contributes to high voltage performance while the R3m/P2/m/P3m1 phase contributes to structural stability, achieving a synergistic effect that resolves the technical contradiction.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If the P63mc crystalline phase structure is used to increase operating voltage, then the energy density is improved, but the cycle performance deteriorates due to volume expansion and shrinkage

Engineering Contradiction:

Improveoperating voltageVSAvoidcycle performance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The positive active material is segmented into a first region with P63mc structure for high voltage operation and a second region with R3m/P2/m/P3m1 structure for structural stability. This segmentation allows the high-voltage P63mc region to operate effectively while the stable second region compensates for volume changes, improving cycle performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent controls the area ratio between the first region and second region within a specific range (0.2-0.8 for the second region), optimizing the balance between high voltage performance and structural stability. This parameter control ensures that the material maintains both high operating voltage and good cycle performance.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If the second structure with low expansion or shrinkage is introduced to improve stability, then the structural stability is improved, but the capacity is reduced due to delithiation time difference

Engineering Contradiction:

Improvestructural stabilityVSAvoidcapacity

Core Design Contradiction:

Stability of the object's compositionVSQuantity of substance

Solution Approach 1:

Different regions of the positive active material are assigned different qualities: the first region has P63mc structure optimized for high voltage and capacity, while the second region has R3m/P2/m/P3m1 structure optimized for structural stability. The local quality of each region is tailored to its specific function, achieving overall optimization without sacrificing capacity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The composite structure combines two crystalline phases with complementary properties. The P63mc phase provides high capacity and voltage, while the R3m/P2/m/P3m1 phase provides structural stability. The synergistic combination maintains high capacity while improving stability, resolving the contradiction between these two parameters.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS20240282940A1Positive active material, positive electrode plate and electrochemical device containing same, and electronic device

Publication Date: 2024.08.22 NINGDE AMPEREX TECHNOLOGY LTD

AI summary

A positive active material, where a cross-section of the positive active material includes a first region and a second region. The first region has a first structure belonging to a P63mc crystalline phase structure. The second region has a second structure belonging to at least one of the following crystalline phase structures: R3m, P2/m, or P3m1. An area ratio between the first region and the second region is 1.8 to 5.4. By controlling the crystalline phase structure and the area ratio of the first region and the second region, the problems of volume expansion and shrinkage of the positive active material during deintercalation and intercalation of lithium can be alleviated, thereby reducing the thickness change rate of the positive electrode plate, and improving cycle performance of the electrochemical device at high voltage.